[Coco] [coco] video signal generation

[Richard Atkinson]

Just one thing I'd check. Are you terminating the video signals properly?
Your filter might be acting partly as a terminator, and without termination
the rise and fall times could be longer.

Richard


On 1/5/07, RJRTTY at aol.com <RJRTTY at aol.com> wrote:

>

> People

>

> I have  been struggling with a problem with my converter for a while

> and I need some  information.

> Does anybody know the details of how the GIME  generates a

> RGB video signal?   The problem I am having is that  while 80 col

> text on the green channel is clear and sharp, 80 col text on the  red

> shows

> some video degradation and 80 col text on the blue channel is  completely

> illegible.

>

> What I am thinking is that the GIME generates the  green channel first,

> the

> red channel second and the blue channel  last.   Is this correct?

> Another

> strange thing is that  80 col text in any color combination that has even

> a

> little green in it shows  up well but if you look at 80 col. text using

> pure

> red or blue as the  foreground or backround you get a wierd kind of video

> smearing.

>

> I  already have a solution.  If a low pass filter is placed in the input

> channels

> the 80 col text shows up well in all color combinations.    In other words

> I

> had

> to DECREASE the bandwidth of the converter in order to  get acceptable

> results.   It seems that the quality of the video  signal coming out of

> the

> GIME in the coco3 is only slightly better than the  old monitors could

> display

> and the high bandwidth of my converter is just too  much for the signal

> showing it "warts and all".

>

> I don't know about the  rest of you but purposely degrading the converter

> to

> approximate the  perfomance of the old monitors just seems wrong to

> me.  The

> image does  soften a tiny bit with the filters but not enough to notice if

> you

> were not  already looking for it or directly comparing it to

> an  unfiltered

> converter.

>

> Does anybody know what is going on with the  conversion process in the

> GIME to cause this?

>

> TIA

> Roy

>

>

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